DHT Heater Group Buy notes.

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Nick
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Re: DHT Heater Group Buy notes.

Post by Nick » Mon May 21, 2018 10:07 am

To quote Andrew
The TLV431 should just drop in, the voltage pre-regulator, the LD1085, is referenced from the TL431
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Re: DHT Heater Group Buy notes.

Post by Andrew » Mon May 21, 2018 10:31 am

Nick wrote:
Mon May 21, 2018 10:07 am
To quote Andrew
The TLV431 should just drop in, the voltage pre-regulator, the LD1085, is referenced from the TL431
Yep, the whole unit is referenced off the TL device, no need for other changes.
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RhythMick
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Re: DHT Heater Group Buy notes.

Post by RhythMick » Mon May 21, 2018 1:02 pm

Ok I'll build a 26 version as soon as the TLV431 arrive and report back. Thanks.

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Re: DHT Heater Group Buy notes.

Post by RhythMick » Mon May 21, 2018 9:34 pm

Is the Vref an internal parameter of the device?

My bad. For some reason I thought it was set externally. Probably because a pin is labelled REF and the datasheet diagrams show Vref external to the device. Of course REF is the voltage at the resistor junction. Doh.

Shows how little I know. I'll get me coat...

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Re: DHT Heater Group Buy notes.

Post by Andrew » Tue May 22, 2018 3:04 pm

The TL series have internal references, the output of the actual device is relative to this reference, which in turn is set by the potential divider on the REF pins.

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Re: DHT Heater Group Buy notes.

Post by RhythMick » Tue May 22, 2018 6:08 pm

Thanks Andrew, the penny dropped last night. Just my inexperience.

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Re: DHT Heater Group Buy notes.

Post by RhythMick » Thu May 24, 2018 8:18 pm

26 board working perfectly thanks.

LD1085P and D44H11 mounted to heatsink remotely and wires running from legs to terminal blocks to PCB vias.

Single heatsink, ambient temperature was 20 degC now 50 after about 5 minutes. Watching to check its stable. When mounted in the amp the heatsink will be mounted on copper sheet.

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Re: DHT Heater Group Buy notes.

Post by RhythMick » Thu May 24, 2018 8:32 pm

Multimeter measures 115mV AC at the simulated filament (resistor). What's normal? Might be better scoping it.

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Re: DHT Heater Group Buy notes.

Post by Andrew » Tue May 29, 2018 8:30 pm

RhythMick wrote:
Thu May 24, 2018 8:32 pm
Multimeter measures 115mV AC at the simulated filament (resistor). What's normal? Might be better scoping it.
115mv :shock: that's huge, are you certain it's all ok? The AC component should be tiny, like less than 2mV (from memory) please have look at the FFT graph/imagess in the group buy for reference.

Andrew
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Re: DHT Heater Group Buy notes.

Post by IslandPink » Tue May 29, 2018 9:54 pm

Multimeter ? :roll:
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Re: DHT Heater Group Buy notes.

Post by RhythMick » Wed May 30, 2018 9:58 pm

Yeah I'll scope it. Work went crazy just at the wrong time.

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